Means for generating the teeth of irregular gears.



E. R. FELLOWS. MEANS FOR GENERATING THE TEETH a; IRREGULAR ems. APPLICATIQN FILED MAR-11,1914 1,221,432, Patented Apr. 3, 1917.

2 SHEETS-SHEET!- Patented la -(3,1917.

2 satin-slain z.

ALI na ERJBZ Lqwa 1 x u l v UNITED sTATnsrarENr OFFICE.

EDWIN E. FELLOWS, 0F SPRINGFIELD, VERMONT, ASSIGNOR. TO THE FELLOWS GEAR SHAPER COMPANY, OF SPRINGFIELD, VERMONT, A CORPORATION OF VERMONT.

Specification of Letters Patent.

Patented Apr. 3, 1917.

Application filed March 11. 1914. Serial No. 824,029.

To all whom it may concern:

Be it known that I, Eowrx R. FnLLows, a

citizen of the United States, and resident of Springfield, in the county of Vindsor and State of Vermont, have invented certain new and useful Improvements in Means for Generating the Teeth of Irregular (tears, of which the following is a specification.

The presentinvention relates to the art, heretofore developed by myself, of generating and cutting teeth in a gear blank by the operation of a planing cutter having peripheral projections similar to the teeth of a spur gear. which is reeiprocatcd across the edge of the blank so as to cut tooth grooves or spaces,

and is rotated simultaneously with the blank to generate the curves. of the teeth thus formed in the worlc 1n the art as heretofore practised the cutter and the work or gear blank are rotated about fixed axes; that is, such axes a re at an ini'ariable distance apart while the cutting progresses. after the cutter has been l'ed to the proper depth inthe work. The objeetof thepresent invention is to provide a cutter capable of generating and cut ting all, or a considerable portion of. the teeth of an irregular gear in the manner indicated without requiring the distance between its axis and the rotational axis of the work to be altered, such cutter having tooth-like peripheral projections so forn'ied and positioned with respect to its axis that the teeth which they generate and cut in the work are adapted to mesh with a gear of regular form. f In order to explain more fully the purpose of the invention and the principles of the means in which such invention is em-' such axis. By axis in this connection I' mean the point within the circuit of the pitch line of the gear about which either the gear isdesigned to rotate when arranged for rotation, or a pinion meshing with the gear is designed to revolve, when the gear is held stationary and the pinion is caused to travel in a planetary manner about it. Such an irregular gear h 15 been termed in the art a multi-lobed gear and will be so termed hereafter in this description. The pinion with which the n'lulti-lobed gear is required to mesh is a pinion of regular form, having its teeth all alike and equally spaced upon the pitch circle, sucii pinion being termed tor the. purposes of this description a standard pinion. In the. running of such a geared couple one of the members, ordinari y the pinion, must ha e a movement toward and from the axis 01 the other member accord ing as the teeth of the irregular gear are nearer to or falther from the axis of the gear. The multi-lobed gear may ha to many shapes and fonts according to the use :for which it is designed, and may have either external or internal, teeth. What-ever its form, however, its teeth, or $OJIIGVOIE them, are irregular in shape in order to mesh with the regular teeth of a standard pinion, and they are necessarily so on account of the fact; that the pitch line onwhich the gear teeth are located varies in its distance from the axis of the gear and is curved about other centers than such axis. The end served by the present invention is to provide a cutter having toothlike projections which are so shaped, and located at such distances from the axis of the cutter, as to be capable when the cutter and gmr blank are rotated or indexed about fixul axes, of. generating the teeth on one of the lobes of the irregular gear in such form that the teeth of the gear will be conjugate to, and so capable of meshing properly with, the teeth of a standard pinion,

In the accompanying drawings I have "shown two different forms of irregular, or

multi-lobed gear, each adapted to mesh with the standard pinion, and in connection therewith I haveshown cutters having peripheral projections shaped so as to generate properly the curves ir the teeth of a lobe of each gear. The torn s of irregular gear illustrated are simply two of the many forms which such a gear might have and are chosen to illustrate the variety of forms in which the essentials of the inventiommay be embodied without attempting to show all of such forms.

Figurel is a plan view of a geared pair consisting of a standard pinion and an irregular gear of tiree lobes, such lobes being symnietrically spaced about the axis of the gear and being similar to one another.

Fig. 2 is a view showing that part of the irregular gear which is icprcsented as meshing with the pinion in Fig. 1. and showing also the cutter which is capable of generating and cutting the teeth of the gear.

Fig. 3 is a plan view of another form of irregular gear and of the cutter conjugate thereio in operative relationship with the teeth which it is adapted to cut.

Fig. -1- is a plan view on an enlarged scale of the cutter illustrated in Fig.

Fig' 5 is a cross section on line of Fig. 4.

Fig. 6 is a fragmentary elevation of part of the gear cutting machine in which my im proved cutter is used, showing the cooperative relationship between the cutter and work.

The sa me reference characters indicate the sameparts in all the figures.

Referring to Fig. 1, 10 represents a standard spur pinion having regular teeth each of which is exactly like every other one. 11 represents an irregular or multilobed gear adapted to mesh with, and to drive or be driven by, the pinion 10 and rotating about its geometric center 12. This gear is an external spur gear of three equal and symmetrical lobes, and the pitch line 13 on which the teeth are'spaced is irregular, that is, unequally distant at different points from the center of rotation of the gear. Th"-v teeth 15 of the-gear are conjugate to the teeth 16 of the pinion see-as to make proper rolling contact with the latter teeth when rotating in'either direction. In consequence the teeth 15 are irregular and vary more or less from one another, certain of the teeth being symmetrical and regular while others are unsynn'nctrical. Those teeth which are on parts of the pitch line tangent to an arc concentric with the center of the gear are symmetrical, while the teeth on eccentric parts of the pitch line are unsyimnetrical, the lack of syn'imctry being particularly n'iarlied in the tooth 15 and those adjacent thereto. It will be seen that the curve of one side of the tootlrlo is flatter than the curve of the other side of the. tooth. and this is true to a greater or less extent to all those teeth which are on eccentric parts of the pitch line.

The purpose of the present invention r; to furnish a cutter. which, when o| )c.r ated asa planing tool and also rotated about a lixcd axis, while the gear blank is rotated 'inunison about a fixcd axis. will generate the curves in the teeth 15, 15", etc, of the gear 11. it is my purpose to provide a cutter which may beused.in=machine's of the gem-rill character of that shown in my prior Patent 1,028,343, in which the spindles of the cut--- ter and \\"-':'l\' holder are at an invariable tance apart during the progress of the cutting operation after the depth feed has been completed, wherefore I have produced a cutter of which the peripheral projections are more or less distant from the indexing axis. in complement to the varying eccentricity of the pitch line of the gear, and are variously formed accordingly so. as to give the required form to the sides of the teeth out in the gear blank. As these projections of the cutter are somewhat similar in form to gear teeth, and have been termed teeth in prior patents relating to this art, I will use this term in the further description of these parts of the cutter. It is to be understood that the edges of the teeth at one side or face of the cutter are formed as cutting edges so that the cutter may act as a planing tool when moved across the face of the work, as described in my prior Patent 1,028,343, and others. The cutter conjugate to the gear 11 is shown in Fig. 2 and is designated 17. It will be seen from inspection of this figure that the teeth of the cutter vary from one another in formand also in distance from the axis, the tooth 18 being the nearest to the axis' of the cutter and having the widest end, and the tooth 18 being farthest from the axis and having its end face reduced to practically a point, the intermediate teeth being more or less distant and having narrower or wider end faces accord-- mg to their relation to the teeth 18" and 18.

The particular cutter illustrated'in this figure is symmetrical on opposite sides of the diameter-A, B, since the cutter is intended to generate teeth on a gear of which the lobes are symmetrical and equal. .Th-is cutter is able to cut all of the teeth on the gear 1.1 without requiring the axis of either the gear' on the cutter to be shifted, because the irregularities of the gear lobes are no greater than the irregularity of the cutter. The sev eral teeth of the cutter are respectively conjugate to corresponding teeth in each lobe of the gear, and the cutter makes as many rotations"in generating all the teeth of the gear as there are lobes to the gear, in this casethree. I

Figs. 3 and 4 show an internal gear 10 having four equal and symmetrically arianged lobes. and flSSUCjtltHl therewith is a cutter-20 having teeth 21 which are designed to form the teeth 22 of any one of the lobes of the gear. In this gear the distz'incesbetween, the approximate centers of curvature of the lobes and the geometric. center 23 of the gca are so great, that it is impossible to gcnc'ralc and cut an of the teeth of the gear or even of one lobe by rotating. the gear about its geometric center, therefore.thc gear is rotated in cutting the lcclh 'of' each lobebe in operative relationship as shown in Fig. 3. When the gear is in this relation to the manner usual with machines of the type shown in my patents aforesaid, during the progress of the succession of cuts made by the cutter. The curvature of the pitch line of the lobe oi the gear is not exactly concentric with the point it, but varies somewhat to either side of an arcdescribed about the point 24 as a center. The teeth 21 of the cutter 20 arecorrespoiulingly more or less distant from the axis of the." cutter and shaped so that the, teeth they cut in the gear blank will be. conjugate to the teeth of a regular pinion which are all at the same distance from the center of the pinion. The gear blank is rotated about the center 24: until as many of, the teeth in one lobe are cut as can be made by the cutter 20, and then the work holder is shifted or indexed about theaxis 2 to bring the centers 25, 2t) and 27 successively into the generating axis, the gear being rotated about each of these centers 2.3, 2H, and 27 in turn while teeth on the lobes of which these points are respectively the generating centers are act. The result accomplished by theuse cut.

The irregular gears shown in Figs. 1 and .4 represent the two different cases which can arise in the operation of. gear cutting according to my present invention. In one of thesecases the gear blank. is rotated about its own center and the teeth of the cutter are sufiiciently irregular in position to meet the extremes of irregularity in the pitch line of the gear blank. In the other case the gear blank is not rotated about its own center, but about different centers which are nearly the centers of curvature of the several lobes of the gear. All other forms and shapesof gear than these two here illustrated come under theone or the other of ternal In each case the critter is conjugate to the teeth of one lobe of the gear with teeth distant from tlie generating axis according to the irregularity ot the part of the gear blank on which they respectively of my improved cutter is to produce an irregular gear of which the teeth are conjugate to the teeth of a standard pinion which is free to move, or with respect to which the irregular gear is free to move, in such a way that the normal distance from the axis of the pinion to the pitch line of the gear is always the same. Thecutter which produces this eflt'ect is one having its teeth at varying distances from its of rotation and conjugate to the teeth of the irregular gear.

In Fig. 6 the blank for-the irregular gear 19 is indicated roughly as mounted on a work holder 28 rotating about the axis of shaft 30. The work holder 28 carries a plate 31 to which the gear blank is fixed, said plate being adjustable with respect to the holder 28, about its center 29 which is in linewith the center of the gear blank. 32 represents tlu spindle, to which the cutter 20 is secured anil by which the latter is reciprocated and iotated. This diagran'nnatic representation (f the relation between the cutter 20, gear blank 19 and work holder, is not intended t) be taken as limiting my invention to any particular machine, but is given to aid in the explanation of the essen tial principles of the invention. f

It will be evident from the foregoing description that the cutter of a series of iormcd cutters, each of the tooth-like projections 18 of the cutter shown in Fig. 2, and 21 of the cutter shown in Figs. 4' and 5,being such a formcdcutter, and that these several projections or' eutting elements are arranged on a curved pitch line on the body of the cutter in a way somewhat similar to the manner in which the teeth of a spur gear are arranged on the pitch line of the gear. Each one-of these cutting elements is capable of cutting in a particular part of the getr blank a groove conjugate to the tooth of a standard pinion, when given a rotatory generating movement about an axis which is unequally distant from different separated points in the said pitch line; that is an axis other than the approximate center of curvature of the pitch line. Inthe apparatus shown in Fig. 6, which illustrates as nuch of a standard gear cut ting machine as is necessary to show the manner in which my cutter is employed to accomplish the results above desc died, the spindle 3-2 is a means for bothirotating the cutter about its generating axis and for moving the cutter along such axis to give therequired cutting movements thereto; and

consists in effect the shaft 30 is a means for giving the work a simultaneous generating movement about an axis at a iixed'distance from the axis whereon the cutter is rotated. The shaft 30 and spindle I52 together constitute a means for 'producing relative cutting movements between the cutter and the blank.

It will be understood that the method carried out in cutting both types of gears illus trated in the drawings is essentially the same but with certain variations; these being mainly that the gear blank shown in Fig. 1'is given its rotatory generating movement about its geometrlc axis, while in the case of the gear shown in Figs. 4 and 6 the gear is given an lncomplete rotation about the approximate center of curvature of one lobe in cutting the teeth on such lobe, and is .then indexed Llld given a further generating rotation about the approximate center of another lobe, this indexing and further rotation being continued "until the teeth are cut in all the lobes of the gear. The term geometric axis, as used in the foregoing descri 'ition is intended to be synonymous with the axis about which either the gear is designed to be rotated when in use or the axis about which a pinion meshing with the gear is designed to revolve.

lhe term irregular and words of like import used in the description of the "ear and cutter are. intended to include any orm of gear or cutter in which the pitch line of its teeth or tooth-like projections is otherwise than concentric with the axis about which the gear is designed to be rotated in use, or the entter to be rotated when generating the teeth which it cuts. As so used such terms have no-relati n whatever to symmetry or lack of symmetry. and they include forms which are symmetrical on opposite sides of a median line as well as forms which are not symmetrical.

'hat 1 claim and desire to secure by Letters Patent is: v

1. A cutter for gear cutting machines having a peripheral series of teeth, the cutting edges of which are shaped differently from .one another and are located at different distances from the axis of rotation of the cutter.

2. A cutter for gear cutting machines having a series of peripheral tooth-like projec'- tions and adapted to generate and cut teeth in a blank, said tooth-like projectionslieing arranged on a pitch line which is otherwise than concentric with the axis about which the cutter is adapted to be rotated in generating tooth curves."

'3. A cutter for generating and cutting teeth in an irregular gear, such cutter having formed cutting elements arranged in a curved irregular pitch line. I

4. A planing cutter for generating and cutting teeth in an irregular gear, said outter having tooth-like cutting elements on its periphery arranged on a curved line, being operable to cut in a substantially axial direction, and having an opening for receiving the" spindle or arbor on which said'cutter is adapted to be mounted, .such openln being eccentric to the approximate center 0 CUI'VH'.

ture of a line passing through corresponding points in all the cutting elements.

A cutter constructed for generating and cutting in a gear on an irregular pitch line teeth conjugate to a standard pinion, said cutter having peripheral cutting elements of which the cutting edges are enera'lly similar to the outlines of stan ard gear teeth, but vary from exact identity with such teeth, and different elements being located at ditferent distances from the axis of said cutter.

6. A cutter for generating and cutting tooth forms in an irregular gear, said cutter .lieiug of dislelike form having an aperture whereby it may be mounted upon a holding spindle, and having peripheral cutting elements at respectively different distances from the center of said aperture, or cutting edges of such cutting elements having generally the outline ofstandard gear teeth but varying therefrom according to their distances from the axis of said apcrture.

7. A cutter for gear cutting machines having means for centering the same on a spindleor arbor and having peripheralcutting elements shaped as complete gear teeth ar-- ranged in a line which is irregular with respect to the axis of said e'entermg means.

8. A cutter for gear cutting machines having a. peripheral series of teeth arranged on an irregular pitch line.

9. A cutter for gear cutting machines having a peripheral series of teeth arranged on an irregular pitch line, the successive teeth being diflerent in'form from one another.

10. A cutter for gear cutting machines having a peripheral series of teeth arranged on an irregular pitch line, the successive teeth being different in form from one another and the opposite sides of certain teeth being unsymmetrical.

In testimony whereof I have aflixed 'my signature, in presence of two witnesses.

' EDWVIN R. FELLOWS.

Witnesses:

.1). \V. MILLER, R. M. l urmws. 

